The present invention relates to a novel process for making acrylated polymers and, more particularly, to a process for the acrylation of limoneneoxide-functional silicones so as to produce novel photosensitive compounds useful for making release coatings, optical fiber coatings and other silicone coatings.
A variety of acrylic and methacrylic functional siloxane monomers and polymers subject to photocure upon irradiation with ultraviolet light are known in the art.
Nordstrom et al., U.S. Pat. No. 3,650,813, discloses an acrylic-siloxane paint binder resin that is crosslinkable with vinyl monomers. Such binder is produced in a two step reaction wherein (1) a siloxane having two or more hydroxy or alkoxy functional groups per molecule is reacted with a hydroxy functional copolymer of acrylic monomers, and thereafter (2) the reaction product of the first step is reacted with a C.sub.5 to C.sub.12 monohydroxy acrylate, e.g., the monoester of a C.sub.2 to C.sub.8 diol and acrylic or methacrylic acid.
Ohto et al., U.S. Pat. No. 3,865,588, describes a planographic plate which employs acryloxy functional silicone polymers. Patentees teach that such acryloxy functional polymers can be prepared by the condensation reaction of an acryloxy containing silicon monomer with a siloxane polymer or silane diol, preferably in the presence of a well known catalyst such as sulfuric acid, phosphoric acid, trichloracetic acid, isopropyl orthotitanate, dibutyltindilaurate, or sodium ethylate.
Martin, U.S. Pat. No. 3,878,263, teaches that acrylate functional silanes or siloxanes may be prepared by the addition of a compound of the formula ##STR1## where G is an unsaturated radical to a compound of the formula ##STR2## ps where Z is an OR.sup.1, R.sup.1 or OSiR.sub.3.sup.1 radical, R and R.sup.1 are monovalent hydrocarbon radicals, and e equals 0 to 2. Such addition reactions are said to be preferably carried out in the presence of a platinum catalyst.
Tanaka et al., U.S. Pat. No. 4,139,538, discloses the preparation of methyldi(trimethylsiloxy) silylpropylgylcerol methacrylate by reacting methyldi(trimethylsiloxy) silylpropyl oxypropylene oxide with methacrylic acid in the presence of a catalyst such as potassium hydroxide, trimethylbenzylammonium chloride, triethylbenzylammonium chloride or triethylamine.
Pigeon, U.S. Pat. No. 4,290,869, provides photopolymerizable organopolysiloxane compositions prepared by reacting an .alpha.,.omega.-dihydroxydiorganopolysiloxane and an alkoxysilane monomer having acryloxy groups bonded thereto.
Sato et al., U.S. Pat. No. 4,293,397, describes photocurable organopolysiloxane compositions which comprise the reaction product of an amino-terminated diorganopolysiloxane and glycidyl acrylate or glycidyl methacrylate admixed with a photosensitizer.
Carter et al., U.S. Pat. No. 4,293,678, discloses acrylated epoxy silicones that are produced by the reaction of acrylic acid or methacrylic acid with an epoxy silicone. Suitable epoxy silicones are represented by the general formula EQU M--D.sub.x --D'.sub.y --D".sub.z --M
wherein M is an R.sub.3 SiO.sub.0.5 group, D is an ##STR3## D" is an ##STR4## D' is an ##STR5## group or an ##STR6## m is an integer from 0 to 25, n is an integer from 0 to 25, x is an integer from 0 to 100, y is an integer from 1 to 5 and z is an integer from 1 to 10. Other epoxy silicones having an oxirane group directly or indirectly attached to the siloxane backbone are also said to be effective. Carter et al. further disclose that 1,4-diazabicyclo (2.2.2) octane is particularly effective as a catalyst for the reaction. Other useful catalysts are said to include p-toluene sulfonic acid, methane sulfonic acid, trifluoroacetic acid, morpholine, tributylamine and benzyldimethyl amine. This disclosure is incorporated by reference into the instant specification.
Koerner et al., U.S. Pat. No. 4,306,050, relates to a process for providing UV curable silicone compositions by reacting an organopolysiloxane having SiCl groups with pentaerythritol triacrylate or pentaerythritol trimethacrylate.
Eckberg in copending U.S. patent application Ser. No. 375,676, filed May 6, 1982, now allowed, U.S. Pat. No. 4,576,999, discloses a polyorganosiloxane containing units of the formula ##STR7## where R is hydrogen or a C.sub.1-3 alkyl radical and G is, independently, a C.sub.1-3 alkyl radical, an epoxy functional organic radical or from 2 to 20 carbon atoms, or an acrylic functional organic radical of from 2 to 20 carbon atoms, with at least one polymer unit being epoxy and/or acryloxy functional. Methods for making such compositions are also provided.
One disadvantage of several of the aforementioned acryloxy functional compositions is that they lack hydrolytic stability. Another disadvantage suffered by some of the foregoing compositions is that their acrylic substituents can only be bonded to terminal silicon atoms or to silicon atoms on the polysiloxane chain by way of an SiOC linkage. Still another disadvantage of prior art compositions is that they are often colored, murky fluids, which limits their depth of cure because ultraviolet light cannot penetrate such opaque fluids.